Non-impact keyless chuck

ABSTRACT

A non-impact keyless chuck suitable for use with manual or powered drivers is disclosed. The chuck comprises a body which carries a rotatable split nut having a relatively fine thread and a plurality of slidable jaws, which may be identical, driven by the rotatable nut. An anti-friction bearing is disposed between the rotatable nut and a bearing thrust ring mounted on the body. A clutch or torque limiting mechanism is provided to limit the tightening torque to a predetermined value while the loosening torque may be limited or unlimited. The front sleeve, and rear sleeve, if used, may be formed from a structural plastic to reduce manufacturing costs. A relatively soft elastomeric grip boot may be placed on the front sleeve to improve the grip and temporarily restrain and center the tool during chuck tightening or loosening operations. A relatively soft elastomeric grip boot may also be placed on the rear sleeve, if used.

This is a continuation of application Ser. No. 08/704,418 filed Aug. 20,1996, now U.S. Pat. No. 5,924,702, which is a continuation ofapplication Ser. No. 08/476,896 filed Jun. 7, 1995, now U.S. Pat. No.5,573,254, which is a continuation of application Ser. No. 08/322,356filed Oct. 13, 1994, now U.S. Pat. No. 5,452,906, which is acontinuation of application Ser. No. 08/234,227 filed Apr. 28, 1994, nowabandoned, which is a continuation of application Ser. No. 08/099,160filed Jul. 29, 1993, now U.S. Pat. No. 5,330,204, which is acontinuation of application Ser. No. 07/884,205 filed May 18, 1992, nowU.S. Pat. No. 5,253,879, which is a divisional of application Ser. No.07/449,722 filed Dec. 11, 1989, now U.S. Pat. No. 5,125,673.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to drill chucks for use with hand drills or withelectric or pneumatic power drivers. More particularly, it relates to achuck of the keyless type which may be tightened or loosened by hand orby actuation of the driver motor.

2. Prior Art

Both hand and electric or pneumatic tool drivers are well known.Although twist drills are the most common tools used with such drivers,the tools may also comprise screw drivers, nut drivers, burrs, mountedgrinding stones and other cutting or abrading tools. Since the tools mayhave shanks of varying diameter or the cross-section of the tool shankmay be polygonal, the device is usually provided with a chuck which isadjustable over a relatively wide range. The chuck may be attached tothe driver by a threaded or tapered bore.

A wide variety of chucks has been developed by the art. In the simplestform of chuck, three jaws spaced circumferentially 120° apart from eachother are constrained by a conical body threaded onto the drive shaft sothat rotation of the body in one direction relative to the drive shaftforces the jaws into gripping relationship with respect to thecylindrical shank of a tool while rotation in the opposite directionreleases the gripping relationship. Such a chuck may be keyless if thebody is rotated by hand. However, because the tightening or looseningtorque which may be applied directly in a hand operation is limited, theart developed the so-called three-jaw geared chuck. This designovercomes the principal problems in the earlier design by providingguideways in the chuck body to control more accurately the motion of thejaws and teeth on the jaws which mesh with a gear driven nut mounted onthe chuck body. The gear is actuated by a pinion formed on a separatekey which may be rotated in a bearing hole formed in the chuck body.

The three-jaw geared chuck is, or can be, a high quality precision toolwhich can exert a relatively large gripping force on the tool. However,the separate key may easily be misplaced or accidentally left in thechuck when the driver is actuated, thus possibly leading to somepersonal injury. In addition, the chucking or unchucking operation is atwo-handed procedure which is time consuming.

To overcome these perceived disadvantages of the key operated gearchuck, various keyless chucks have now been developed. Such keylesschucks fall broadly into two classes: impact and non-impact chucks.Impact chucks employ means to apply a series of impacts to the nut so asto tighten or loosen the jaws. In the non-impact design, manual ormechanical means are used to restrain one member of the chuck while atorque is applied to another member of the chuck either manually or bythe power driver to move the nut relative to the jaws. A keyless chuckof the impact type is disclosed in McCarthy U.S. Pat. No. 4,840,387while the prior art cited therein illustrates keyless chucks both of theimpact and the non-impact variety.

SUMMARY OF THE INVENTION

In accordance with the present invention, a keyless chuck of thenon-impact type is provided. The invention employs an anti-frictionbearing interposed between the nut and the body to decrease the frictionlosses in the mechanism so as to increase the effective tighteningtorque. The bearing thrust ring is formed separately from the bodymember and pressed thereon so as to increase the effective diameter ofthe body while minimizing the machining requirements. The principalload-bearing parts of the chuck, i.e., the jaws, body, nut, bearing andbearing race are formed from metal while the front and back sleeves andrelated parts may be formed from plastic materials so as to reduce thecost and permit customizing of the chuck. Additional features of theinvention include an elastomeric grip boot for the front sleeve whichalso functions as a bit holder and centering device, a one-way torquelimiting clutch for limiting the tightening torque while permittingpositive loosening torque, and a torque-limiting clutch which providesgreater loosening torque than tightening torque. In accordance with aprocess feature of the invention, the three jaws are identical withrespect to their nut engaging threads and the eccentricity of theirengagement is overcome by a grinding procedure following assembly of thechuck.

DESCRIPTION OF THE DRAWINGS

Further objects and advantages of the invention will become apparentfrom the following detailed description and the accompanying drawings inwhich:

FIG. 1 is a perspective view of a keyless chuck in accordance with thepresent invention,

FIG. 2 is an enlarged longitudinal view, partly in section taken alongline 2—2 of FIG. 1,

FIG. 3 is a transverse cross-sectional view taken along line 3—3 of FIG.2,

FIG. 4 is an enlarged longitudinal view, partly in section, of analternative form of the invention including a torque limiting mechanismand a bit retaining and centering device,

FIG. 5 is a transverse cross-sectional view taken along 5—5 of FIG. 4and showing the torque limiting mechanism,

FIGS. 5A, 5B, 5C, 5D, 5E, 5F, AND 5G are fragmentary cross-sectionalviews showing alternative forms of the torque limiting mechanism,

FIG. 6A is a plan view of a toothed retainer disc shown in FIG. 4,

FIG. 6B is an edge view, of the retainer disc shown in FIG. 6A,

FIG. 6C is an edge view, partly in section, of an alternative form ofthe retainer disc having a beveled rim,

FIG. 6D is a plan view of a toothless retainer disc having a beveledrim,

FIG. 6E is an edge view, partly in section, of the retainer disc shownin FIG. 6D,

FIG. 7 is an enlarged longitudinal view, partly in section, of a furtheralternative form of the invention which is particularly adapted formanual operation,

FIG. 8 is a fragmentary view taken along line 8—8 of FIG. 7 and showingthe clutch mechanism.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1, there is illustrated a chuck 10 in accordancewith the present invention. The chuck 10 includes a front sleeve member12, an optional rear sleeve member 14, a body member 16 and jaws 18.

As shown more clearly in FIG. 2, the body member 16 is generallycylindrical in shape and comprises a nose or forward section 20 and atail or rearward section 22. The nose section 20 is, preferably,chamfered at its outer end. An axial bore 24 is formed in the nosesection 20 of the body member 16. Axial bore 24 is somewhat larger thanthe largest tool shank which the chuck is designed to accommodate. Athreaded bore 26 is formed in the tail section 22 of the body 16 and isof a standard size to mate with the threaded drive shaft of a powered orhand driver (not shown). The bores 24, 26 may communicate at the centralregion 28 of the body member 16. If desired, the threaded bore 26 may bereplaced by a tapered, unthreaded bore of a standard size to mate with atapered drive shaft.

Passageways 30 are formed in the body member 16 to accommodate each jaw18. Preferably, three jaws 18 are employed and each jaw 18 is separatedfrom the adjacent jaw by an arc of 120°. The axes of the passageways 30and the jaws 18 are angled with respect to the chuck axis but intersectthe chuck axis at a common point ahead of the chuck body 16. Each jaw 18has a tool engaging face 32 which is generally parallel to the axis ofthe chuck body 16 and threads 34 on its opposite or outer surface. Inaccordance with a feature of the present invention, the threads 34 havea relatively fine pitch, i.e., a pitch greater than 20 threads per inch,e.g., 32 threads per inch, and the threads, preferably, are of thebuttress type though other thread forms may be employed. By employingthe buttress thread form the tightening force applied to the jaw threads34 is substantially axial to the jaw 18 so as to maximize the conversionof the tightening torque applied to the chuck into a gripping forceapplied to the tool shank. The use of a relatively fine pitch threadresults in two advantages for the chuck in accordance with the presentinvention. First, the relatively fine pitch results in a greatermechanical advantage so that a given tightening torque is converted intoa larger gripping force. Second, it becomes possible to useinterchangeable jaws 18 of identical design rather than slightlydifferent jaws that must be selected and assembled as a set. The smalleccentricity which results from the use of identical jaw pieces inaccordance with the present invention can be counteracted by a grindingstep as more fully described below.

A circumferential groove 36 is formed in the body member 16 and extendsinto the passageways 30. A split nut 38 having female threads 40 islocated in the circumferential groove 36 and secured therein by thefront sleeve member 12. The split nut 38 is preferably formed withcircumferential serrations or teeth 44 and the outer edges are providedwith a small chamfer to facilitate press fitting of the split nut 38into the bore 42 of the front sleeve 12. Preferably, the front sleeve isformed from a structural plastic such as a polycarbonate, a filledpolypropylene, e.g., glass-filled polypropylene, or a blend ofstructural plastic materials. The serrations or teeth on the split nut38 assure that the front sleeve 12 will hold the split nut 38 securelywithout being subjected to an excessive hoop stress.

A circumferential race 46, which may be grooved or a flat surface, isformed on the rear face of split nut 38 to accommodate an anti-frictionbearing, for example, ball bearing assembly 48. If desired, the bearingassembly 48 may include a bearing retainer 49 (see FIG. 4) which locatesthe plurality of balls while permitting them to roll. A bearing thrustring 50 is provided with a central hole 52 sized to be press fitted onthe body member 16. One face of the bearing thrust ring 50 has formedthereon a bearing race 54, which may be grooved or flat, against whichthe bearing assembly 48 rides. A plurality of jaw guideways 56 areformed around the circumference of the central hole 52 in the thrustring 50 to permit the retraction of the jaws 18 therethrough. Theguideways are shaped to conform with the toothed area of the jaws 18 soas to reduce or prevent toggling of the jaws 18. To perform thisfunction, the axial length of the guideways 56 must be greater than thepitch of the threads 34 on the jaws 18. The outer circumference of thebearing thrust ring 50 may have formed thereon serrations or teeth 58and the outer edges may be chamfered so as to facilitate pressing of thebearing thrust ring 50 into a bore 60 formed in the rear sleeve member14. The rear sleeve member 14 also contains a bore 62 adapted to matewith the tail section 22 of the body member 16. If desired, the rearsleeve member 14 may be omitted and the front sleeve member 12 extendedto the tail end of the body 16. This alternative is feasible when aspindle lock is provided on the driver or when the driver is used totighten or loosen the jaws.

The circumferential surface of the front sleeve member 12 may be knurledas suggested at 63 or may be provided with longitudinal ribs or otherprotrusions to enable the operator to grip it securely. In like manner,the circumferential surface of the rear sleeve member 14, if employed,may be knurled or ribbed, if desired.

It will be appreciated that the rear sleeve member 14 is fixed to thebody member 16 while the front sleeve member 12 is fixed to the splitnut 38. Thus, relative movement of the front and rear sleeve members 12,14 will cause the jaws 18 to be advanced or retracted, depending uponthe direction of the relative motion. As the bearing 48 is interposedbetween the relatively moving parts, the frictional losses are minimizedand a maximum portion of the applied tightening torque is converted to atightening force on the tool shank. While the chuck of FIGS. 2 and 3 maybe operated manually, it may also be operated by the power driver.

As noted above, the jaws 18 are preferably formed so as to be identicalto each other. In three-jaw geared chucks, it is common practice tooffset the threads proportional to the thread pitch so that when thejaws contact each other they will meet on the axis of the chuck. Bymaking the jaws identical a degree of eccentricity will result but thisis minimized by the fine pitch of the threads. In accordance with thepresent invention, a grinding procedure may be performed after the chuckis assembled to remove the eccentricity resulting from the small axialdisplacement of the jaws relative to each other. When the eccentricityis removed, the centering accuracy of the chuck will be the same as ifcustom sets of jaws had been provided.

Reference is now made to FIGS. 4 and 5 which illustrate an alternativeform of the present invention containing a torque limiting mechanism anda bit holding and centering device. Parts which are substantially thesame as in the embodiment shown in FIGS. 2 and 3 are identified by thesame designators while modified parts are designated with the additionalletter “a”.

In the embodiment shown in FIGS. 4 and 5 a torque limiting mechanism isprovided which produces an audible “click” when the chuck has attainedits maximum tightness. This may be accomplished by providing a toothedannulus 64 having a bore 66 which engages the outside diameter of, orthe teeth or serrations 44 on the split nut 38 so as to lock the splitnut 38 in place. A series of flexible teeth 68 are formed on thecircumference of the annulus 64 which engage ribs 70 formed on thelateral surface of a bore 72 in the front sleeve member 12 a. As mostclearly shown in FIG. 5 the flexible teeth 68 have a sloping forwardedge 68 a which engages the ribs 70 during tightening of the chuck. Whena predetermined tightening torque is reached, the ribs 70 pass over theflexible teeth 68 producing an audible “click.” However, when the frontsleeve 12 a is turned so as to loosen the chuck jaws 18, the ribs 70lock with the teeth 68 to transfer all the applied torque to the splitnut 38.

It will be noted that the front sleeve 12 a extends beyond the nose 20of the body member 16 to the region where the jaws 18 meet in theirfully closed position. A grip boot 74 may be fastened to the frontsleeve 12 a by ribs 76, 78 and prevented from turning relative to thefront sleeve 12 a by longitudinal ribs (not shown). The grip boot 74 ispreferably made from an elastomeric material such as natural orsynthetic rubber and has a relatively small flexible orifice 80 alignedwith the axis of the chuck body member 16. Preferably, the grip boot 74is made from a relatively soft material having a Shore A hardness offrom 40 to 70. The orifice 80 is sized so that it will stretch to gripthe shank of a drill or other tool inserted in the chuck and temporarilycenter and restrain the tool during chucking or unchucking operations.

In the embodiment of the invention shown in FIGS. 2 and 3, the frontsleeve 12 is held in place because it is press fitted to the split nut38. In the embodiment shown in FIGS. 4 and 5 other means are required tolocate the front sleeve 12 a. A circumferential groove 82 is formed inthe nose section 20 of the body member 16 to receive a retainer disc 84which is pressed into the bore 72 of the front sleeve 12 a. FIG. 6Ashows a plan view of the retainer disc 84 having circumferential teeth86 and flexible engaging tabs 88 formed by a series of slots 90 stampedin the disc 84 around its center hole 92. As shown in FIG. 6B, theretainer disc 84 is flat and relatively thin so as to enable it to bepressed on to the body member 16 and turn freely in the groove 82. Theretainer disc 84 is sized so that the teeth 86 firmly grip the bore 72of the front sleeve member 12 a. FIG. 6C illustrates an alternative formof a toothed retainer disc 84 c having a beveled rim 94. FIG. 6D shows atoothless retainer disc 84 d in plan view. Like the toothed retainerdisc 84, the center hole 92 has slots 90 formed around its edge todefine flexible engaging tabs 88. FIG. 6E shows the beveled rim 96 whichforms a deformable gripping member.

As noted above with reference to FIG. 5, the toothed annulus 64 performstwo functions: first, it holds the split nut 38 in place, and, second,it forms one part of the torque limiting mechanism. FIGS. 5A-5Gillustrate a number of alternative designs for the toothed annulus 64.In FIG. 5A the annulus 64 a is formed with a series of axial slots 98located intermediate its inner and outer surfaces. A tooth 100 islocated midway between the ends of each slot 98 which engages with theribs or teeth 70 formed on the bore 72 of the front sleeve member 12 a.The slots 98 provide the flexibility required for the tooth action whilestill maintaining the strength of annulus. In FIGS. 5B-5G furthervariations are shown in the design of the annulus. In FIG. 5B theannulus 64 b is provided with a series of open slots 102 which result ina series of pawls 104 having a tooth 106 at the end thereof whichengages the teeth 70 b on the bore 72 of the front sleeve 12 a. In FIG.5B the tooth 106 has a square profile so that limited torque istransmitted when the sleeve 12 a is rotated in a clockwise directionrelative to the body 16 as viewed in FIG. 5B but unlimited torque istransmitted with counterclockwise rotation. This difference is due tothe asymmetrical shape of the tooth 70 b. FIG. 5C is similar to FIG. 5Bexcept that the tooth 108 has a round rather than a square shape and therear face of the tooth 70 c has correlative shape. FIG. 5D is likewisesimilar to FIG. 5B except that the tooth 110 has a triangular ratherthan a square shape and the tooth 70 d has a correlative asymmetricshape.

FIGS. 5E-5G show modifications of the structures respectively shown inFIGS. 5B-5D. In these modifications the tooth 70 e, 70 f, or 70 g isdesigned to be substantially symmetrical about a radius of the frontsleeve 12 a so that the tightening torque and the loosening torque aresubstantially equal. It will be understood that the torque transmittedthrough the mechanism is principally a function of the angle of thesurface of the teeth 70 and 68, 100, 106, 108 or 110, the coefficient offriction between the teeth, the force required to depress or deform theteeth 68, 100, 106, 108 or 110, and the number of teeth in contact. Thetorque increases as the tooth surface approaches a radius of the frontsleeve, as the coefficient of friction increases, as the stiffness ofthe teeth on the annulus 64 increases, and as the number of teeth incontact increases. By appropriately controlling these variables, thedesired tightening and loosening torque may be predetermined.

Reference is now made to FIGS. 7 and 8 which show an embodiment of thepresent invention which is particularly adapted for manual operation.Again, parts which are substantially the same as in the earlierembodiments bear the same designations while modified parts aredesignated by “a” or “b.” The embodiment of FIG. 7 is characterized bythe location of the torque limiting mechanism in the rear sleeve member14 a. The basic structure of the body member 16, the jaws 18, and thesplit nut member 38 upon which the front sleeve member 12 b is pressedis similar to that shown in FIG. 2 except that a grip boot 74 a isapplied to the surface of the front sleeve member 12 b to enhance thegrippability of the sleeve member. Grip boot 74 a does not provide thetool holding feature shown in FIG. 4 but it is apparent that thisfeature could be added, if desired. The arrangement of bearing 48 andbearing thrust ring 50 a is also similar to that shown in FIGS. 2 and 4except that no serrations or teeth are formed on the outer periphery ofthe bearing thrust ring 50 a. In the embodiment of FIG. 7, the bore 60 ais sized for a sliding fit with the bearing thrust ring 50 a andaccommodates a Belleville or other form of compression spring 112 whichbiases the rear sleeve member 14 a toward a back plate 114 which ispress fitted onto the tail section 22 of the body member 16. As shown inFIG. 8, the back plate 114 may be provided with a plurality of teeth 116and the rear sleeve member 14 a provided with a plurality of radial ribs118. It will be appreciated that during a chucking operation the rearsleeve 14 a will be held while the front sleeve 12 b is turned in aclockwise direction as viewed from the jaw end of the chuck. At apredetermined torque, the ribs 118 will ride over the teeth 116 whilethe rear sleeve 14 a is displaced in a forward direction against thebias of the spring 112. The teeth 116 on the back plate 114 are designedto produce a limited tightening torque and an unlimited looseningtorque. By varying the angle of the teeth faces and the spring rate ofthe compression spring 112 the tightening and loosening torque may bevaried as desired and as explained above. Of course, the teeth 116 andthe ribs 118 may be interchanged, if desired, and various shapes ofteeth may be employed as suggested in FIGS. 5-5G.

The chuck in accordance with the present invention has a number ofadvantages with respect to the ease and cost of manufacture. The bodymember 16 may be machined from a relatively small diameter bar since thebearing thrust ring 50 is made separately and then pressed onto the bodymember. This reduces the machining costs for the body member. Certainparts, such as the split nut and bearing thrust ring may be formed frompowdered metal or stamped or otherwise cold formed with limitedmachining steps. With this design of the load-bearing parts, the moremassive front and rear sleeves may be formed from structural plasticmaterials thereby reducing weight and manufacturing costs whileproviding the ability to customize the chuck through the use of colors,rib shapes, knurling, or identification logos.

The terms and expressions which have been employed are used as terms ofdescription and not of limitation and there is no intention in the useof such terms and expressions of excluding any equivalents of thefeatures shown and described or portions thereof, but it is recognizedthat various modifications are possible within the scope of theinvention claimed.

What is claimed is:
 1. A chuck for use with a manual or powered driverhaving a rotatable drive shaft comprising: a generally cylindrical bodymember having a nose section and a tail section and a firstcircumferential groove formed therein intermediate said nose and tailsections, said tail section having an axial bore formed therein to matewith said drive shaft of said driver and said nose section having anaxial bore formed therein and a plurality of angularly disposedpassageways formed therethrough and intersecting said axial bore andsaid first circumferential groove; a plurality of jaws slidablypositioned in each of said angularly disposed passageways, each of saidjaws having a jaw face formed on one side thereof and threads formed onthe opposite side thereof; a split nut rotatably mounted in saidcircumferential groove and in engagement with said threads on said jaws,said split nut having a first bearing race formed therein; a generallycylindrical front sleeve member fixed on said split nut and overlyingthe said nose section of said body member; an elastomeric grip bootdisposed about an outer surface of said front sleeve member and having afront section extending over said nose section axial bore to define anexpandable orifice concentric with said nose section axial bore andhaving a diameter less than the diameter of said nose section axialbore; a bearing thrust ring fixed on said body member and having asecond bearing race formed thereon and in juxtaposition with said firstbearing race; and an anti-friction bearing disposed between said firstand second bearing races.